Seasonal abundance of ticks collected at US Army Garrison Humphreys, Pyeongtaek, Republic of Korea, 2019-2021

Tick surveillance was conducted annually from February-November 2019-2021 at US Army Garrison (USAG) Humphreys, Pyeongtaek, Republic of Korea (ROK). Three general habitats, cut grasses, uncut grasses + herbaceous vegetation, and young mixed (deciduous and conifer) forest groves, were surveyed using tick drags. Ticks also were collected from Korean water deer, Hydropotes inermis argyropus, killed by vehicles at USAG Humphreys. A total of 53,428 ticks (18,004, 16,921, and 18,503 during 2019-2021, respectively) belonging to two genera and five species were collected by tick drag. Haemaphysalis longicornis (48,880; 91.49%) was the most frequently collected tick, followed by H. flava (2,501; 4.68%), Ixodes nipponensis (2,019; 3.78%), H. phasiana (27; 0.05%), and H. japonica (1; <0.01%). A total of 1,340 ticks belonging to two genera and three species were collected from 20/27 (74.07%) Korean water deer from January-December 2019-2021. Haemaphysalis longicornis (1,138; 84.93%) was the most commonly collected tick, followed by I. nipponensis (184; 13.73%), and H. flava (18; 1.34%). Ixodes nipponensis was collected from Korean water deer throughout the year, indicating that they were active during all seasons in the ROK. Haemaphysalis longicornis adults and nymphs were collected similarly from all habitats during March-November. Haemaphysalis flava was more frequently collected during the early and late seasons when there were relatively low temperatures. Unlike other species, I. nipponensis was collected more frequently in mixed forests from March-June. Adult male H. longicornis accounted for only 0.05% (3 male/5,76 female) of the total number of adults collected by tick drag, while no males (0 male/194 female) were collected from Korean water deer. In contrast, only H. flava males (15) were collected from Korean water deer, while both sexes of I. nipponensis (103 male/75 female) were collected during 2019-2021.